Vehicle hoist

ABSTRACT

A hoist for a vehicle including a lower chassis ( 2 ) adapted for secure placement on and optional general movement about a floor, an upper platform ( 1 ) fitted to said chassis and movable between a first lowered position to a second raised position wherein said hoist is capable of placement underneath a vehicle when in said first position and said platform and chassis remain coplanar during movement between said first and second positions and both said platform and said chassis have a footprint sufficient to allow stable holding of a vehicle when mounted on said hoist characterized in that said hoist is fitted with a locking means for holding said upper platform in said raised position said locking means including an elongate locking arm ( 24 ) pivotally fitted to one end ( 52 ) of said chassis and telescopically passing through a collar ( 25 ) pivotally fitted to the other corresponding end ( 53 ) of said platform wherein said collar has a lock adapted to co-operate with said locking arm, to arrest said telescopic movement and lock said hoist.

This invention relates to hoists and in particular to motor vehiclehoists which are portable and mobile allowing an operator to manuallymove and manipulate an elevated motor vehicle.

BACKGROUND TO INVENTION

The motor vehicle industry, particularly that part of the industryinvolved in maintenance, repair and renovation, has a constant demandfor aids to assist in the manipulation and handling of vehicle bodieswhich cannot be handled confidently without mechanical assistance.

Such aids include lifting devices, mounting devices and holding devicesof various descriptions. Lifting devices range from simple one pointjacks which lift a single point on a vehicle to massive inground fixedhoists which raise the entire vehicle to allow clear standing accessunderneath.

Mounting devices include simple axle stands and ramps to complex jigscapable of rotating a vehicle from a horizontal to a verticalorientation.

Whilst all the previously mentioned devices have clear application anduse in the industry, one of the more frequent requirements in theindustry is to easily manipulate and move a vehicle which may have nowheels, damaged suspension, no engine etc; or move a collection ofvehicles in a confined space, or simply raise an entire vehicle half ameter or so where it stands to allow clear access underneath.

To date, none of the available devices cater for the above range ofhandling requirements. Workshop situations often find vehiclesprecariously placed on four individual axle stands or suspended ontrolley jacks. Inground hoists also present limitations as vehicles arefixed at one place in a workshop until they are mobile of their owncomponentry and the hoist is unavailable for other uses. Inground hoistsare also highly expensive installations.

Other solutions are available including placing vehicles on elevatedtrolleys of a fixed height; however, such devices require the elevationof the vehicle to the trolley height and do not provide a completesolution to the above-described problem.

One object of the invention is to provide an improved vehicle hoistwhich is compact and capable of raising and readily moving a vehiclewithout further mechanical assistance with one operator.

STATEMENT OF INVENTION

In one aspect, the invention provides A hoist for a vehicle including alower chassis adapted for secure placement on and optional generalmovement about a floor, an upper platform fitted to said chassis andmovable between a first lowered position to a second raised positionwherein said hoist is capable of placement underneath a vehicle when insaid first position and said platform and chassis remain coplanar duringmovement between said first and second positions and both said platformand said chassis have a footprint sufficient to allow stable holding ofa vehicle when mounted on said hoist characterised in that said hoist isfitted with a locking means for holding said upper platform in saidraised position said locking means including an elongate locking armpivotally fitted to one end of said chassis and telescopically passingthrough a collar pivotally fitted to the other corresponding end of saidplatform wherein said collar has a lock adapted to co-operate with saidlocking arm to arrest said telescopic movement and lock said hoist.

The lock preferably incorporates a pawl fitted to the pivoted collarwhich may be spring loaded and bias to intercept the travel path of thelocking arm as it passes through the collar. The locking arm may beprovided with a plurality of protuberances or indentations along itslength which are adapted to co-operate with the pawl to arrest anybackward movement of the locking arm and hoist.

The pawl preferably acts through a pivot positioned to allow the pawl toengage the locking arm by an over center motion thereby ensuring thatonce the pawl has engaged a step or indention in the locking arm, it isonly possible to release the pawl if the locking arm has moved forwardso as to allow the pawl sufficient space to again move over center andwithdraw thereby releasing the lock. The hoist may also include wheelmeans to provide mobility to the hoist if required. The wheel means maybe castor systems including a swivel housing fitted to the lower chassiswhich can sit on the floor when the wheels are retracted or optionallyelevate the hoist by the raising of an arm pivoted intermediate on saidhousing where the arm has a wheel fitted at the other end.

The footprint of said hoist is preferably at least 20% of the mountedvehicles wheel footprint.

The hoist may have a substantially rectangular footprint in the lowerchassis and upper platform with raising arms pivotally fitted in theregion of the respective corners of said lower chassis and said upperplatform so as to allow said upper platform to be raised and loweredrelative to said chassis causing said platform to offset forward orrearward during said raising and lowering.

The hoist may be moved between said first and second positions by a ramfitted between a rearward position on said lower chassis and a forwardposition on said upper platform such that activation of said ram causessaid upper platform to simultaneously move forward and up relative tosaid chassis.

The upper platform may be adapted to lay flat against said chassis whenin said first position.

The raising arms may be of equal length and corresponding fitting toeach corner region of the hoist The arms may be provided with steps tolimit the raised position of the hoist to pre-overcentering of saidraising arms.

The invention will now be described in greater detail with reference toone particular embodiment shown in the accompanying representations.

FIG. 1 shows a side view of the collapsed hoist in a lowered position.

FIG. 2 shows a plan view of the hoist.

FIG. 3 shows a side view of the raised hoist.

FIG. 4 shows an end view of the raised hoist.

FIG. 5 shows a perspective view of the raised hoist.

FIG. 6 shows a side view of sliding rubber blocks fitted to the hoist.

FIG. 7 shows an end view of a rubber block.

FIG. 8 shows a plan view of a rubber block.

FIG. 9 shows a top view of the locking means.

FIG. 10 shows an end view of the locking means.

FIG. 11 shows a sectional side view of the locking means.

FIG. 12 shows a side view of the retractable wheel means in a retractedposition.

FIG. 13 shows an end view of the retracted wheel means.

FIG. 14 shows a side view of the wheel means in a raised position.

FIG. 15 shows an end view of the raised wheel means.

LEGEND FOR FIGURES (1) Upper platform. (2) Lower chassis. (3) Cornerimpact cushions. (4) Rubber blocks which seat between vehicle underbodyand (1). (5) Slide channels for (4) which are welded to (1). (6) Wheelmounts which are welded to (2). (7) Twin wheel castor system. (8) Wheelhousing that incorporate 2 roller bearing sets in a swivel head. (9)Raising arms that hinge and join (1) to (2) platforms together at eachend of (9) is greasing point. (10) At each end of the lifting arms (9)is a machined collett to lock arms between (1) and (2). (11) Checkerplate which is welded to (2) and acts as a cover for the hydrauliclinkages. (12) Checker plate which is welded to (1) and acts as a coverfor the hydraulic linkages. (13) Main hydraulic ram which is mounteddiagonally between (1) and (2). (14) Hydraulic hose burst valve, whichis activated when (19) is severed or cut. (15) Position for power sourceeither A) air over hydraulic Power Pack or B) 240 Volt over hydraulicpower pack, or C) 12 Volt (Car battery) over hydraulic power pack. Thisflexibility of power source offers wide application. (16) Checker platecovers to protect (not welded) power pack (15) and also to protecthydraulic line (36) that runs from wheels (37) to main hand pump (17).(17) Small hand pump unit secured under (16) which activates hydraulicrams (37) and the four retractable wheel means. (18) The pull knob andlever to release The Safety Locking Unit (25) and allow the locking bar(24) to lower. (19) The hydraulic hose which runs from (13) to (15).(20) The twin brackets which support and pivots the safety-locking unit(25) from (48). (21) Corner checker plate, which acts as strengtheningbraces on four corners and anti-skid surfaces for (4). (22) Nut-sertsare located in (1) to bolt auxiliary brackets to bench to supportvehicle 8 in total. (24) Locking arm hinged and secured diagonallybetween (1) and (2), with the upper end moving through (25). (25) Collarwhich is hinged (48) and pivoted at it's base to (1). (30) Countersunkbolts secure (6) to (31) to (8) on each of the four wheel means. (31)Spacer plates, designed to give support to (8) and give clearance to(36). (32) Dog-bone shaped arms that hinge between (35) and (34).Pressure from (38) causes (32) to pivot downward giving elevation tohoist. Retraction is by release of pressure from (17) causing (38) torelease allowing (32) to retract. (33) Retaining nut that holds (38) inplace and prevents (38) from over- stroking. (34) Wheel axle thatsecures (7) to (34). (35) Rear axle that pivots (32) to (8). (36)Hydraulic pipes that run inside (2) back to (17). (37) Wheel ram body,which is secured in position by clearance, fit through (8) and pinned to(31). (38) Hydraulic piston that is fixed inside (37) and retained by(33) and radius end sits on surface of (32). (39) Rubber hydraulic sealthat is secured to (38). (40) Lever arm for releasing (46) upward when(1) is descending, lever is activated by pulling (18). (41) Top dustcover that is secured by 6× (42's) to main body (25). (42) Allen Headset screws. (43) Main central shaft by pulling (18), (40) then turns(43) in anti- clockwise direction. This lifts (49), which in turn lifts(47). This is only possible when the hoist is under load and supportedby the hydraulic ram (13). The hoist can never be lowered without thehydraulic ram (13) under load and in place. Until pressure is taken upby (13), (46) will bear up hard against (24) and prevent accidentalrelease. (44) Indentation. (45) Spring to return (46). (46) Main lockingpawl. (47) Shaft to pivot and secure (46). (48) Main hinge lug welded tosafety locking unit (25). (49) Lifting arm pinned to (43), whenactivated will lift (47). If (18) is ever physically let go for anyreason (46) will automatically return to it's position locking up thehoist at that point of descent. (50) Locating pin for (45). (51) Innerreinforcement for (4). (52) Rearward position. (53) Forward position.(54) Bearing face. (55) Indentation face.

DETAILED DESCRIPTION OF THE INVENTION

Referring firstly to FIGS. 1 to 5, the hoist is generally provided witha raisable parrallagram mechanism comprising a substantially rectangularlower chassis 2 which is provided at each corner with a retractablewheel means 7/8 which provides the chassis with general mobility in alldirections across the workshop floor when the wheels are in a raisedposition and if required, allows the lower chassis to sit firmly on aworkshop floor when the wheels have been retracted so as to prevent anyunwanted movement of the chassis or hoist. The hoist is provided with anupper platform 1 of generally rectangular configuration and of similardimensions and footprint to that of the lower chassis. The upperplatform is fitted to the lower chassis and movable between a firstlowered position where the upper platform and lower chassis sitsubstantially on top of the other to a second raised position. The upperplatform 1 and lower chassis 2 are connected by way of four raising arms9 pivotally attached at each respective corner of said upper platformand lower chassis. The raising arms 9 are all of substantially identicallength and accordingly allow the upper platform to be pivotally raisedand lowered in a manner ensuring that the upper platform remainsco-planar with the chassis and accordingly, co-planar with the floor.The relative movement of the upper platform and chassis is effected by amain hydraulic ram 13 which is fitted diagonally between a rearwardposition 52 on the lower chassis 2 and a forward position 53 on theupper platform 1 such that the activation of the ram causes the upperplatform to move both forward and upward relative to the lower chassisthereby effecting the raising of the upper platform and the lifting ofany vehicle positioned on said upper platform.

In order to ensure complete safety in the use of the hoist, the upperplatform is fitted with a locking means comprising an elongate lockingarm 24 which is pivotally attached to a rearward position on said lowerchassis and adapted to pass through a locking collar 25 which ispivotally fitted to a forward position on the upper platform 1. Themovement of the hoist between the raised and lowered positions causesthe locking arm to slide telescopically back and forth through thecollar which is provided with a suitable lock to arrest this telescopicmovement and accordingly arrest the vertical movement of the hoist atany desired position.

Referring now go FIGS. 9 to 11, the locking means can be seen tocomprise an elongate locking arm 24 adapted for telescopic and coaxialmovement through a collar 25. The elongate locking arm 24 has formedalong its length one or a plurality of protuberances or indentations 44which forms steps which are adapted to cooperate with a lock positionedon the collar. The lock takes the form of a ratchet mechanism comprisesa pivoted pawl 46 which is formed in a housing associated with thecollar. The pawl is adapted to be pivoted around pivot point 47 andmanually activated by way of a lifting arm 49 pivoted at a central shaft43 providing external access for release of the paw). The pawl is heldin an engaged position by way of spring 45 which serves to urge the pawlinto a position so as to intercept the indentations 44 of the lockingarm 24. The spring also allows the pawl to act as a ratchet allowing thelocking arm to move through the collar in one direction only until thepawl is released. The movement of the locking arm 24 telescopically andcoaxially through the collar causes the locking pawl to act as a ratchetand successively engage the respective indentations 44. The particularaction and configuration of the locking pawl is such that the bearingface of the pawl 54 which rests against the indentation face 55, isconfigured so as to lockably engage the indentation face when the pawlhas moved over center so as to prevent the locking pawl withdrawingwhilst the bearing face 54 is in contact with the indentation face 55.This arrangement has the effect of allowing the locking pawl to functionas a ratchet while the locking arm is being pushed through the collarduring the raising action of the hoist. However, whilst the hoist is inany position with the locking pawl engaging an indentation 44, it isimpossible to release the locking pawl unless the locking arm has beenpushed forward to some degree to allow sufficient room for the lockingpawl to again move over center and withdraw. This provides an importantsafety feature such that the locking means of the hoist can provide theuser with a confident and perfectly safe way of securing the hoist atany one of a number of raised positions such that the main hydraulic ramand, in fact, all the hydraulic systems can be removed from the hoistonce it is in a suitable raised position with confidence knowing thatwithout the ability to further raise the locking arm 24 (which can onlybe done with the hydraulics in place), it would not be possible torelease the locking pawl from the locking arm and lower the hoist.

Once the hoist has been locked in the desired position, the ram andgeneral hydraulic components of the hoist can be completely removed inorder to ensure that the components of the hoist are not damaged by anyof the actions or environment of a vehicle repair shop includingwelding, spraying and other actions that could otherwise damage thedelicate hydraulics of such a device.

In order to ensure the maximum scope of operation of the hoist, theraising arms 9 are provided with a crank at a first end. The position ofthe crank allows the upper platform to fold down and sit snugly on topof the lower chassis 2 thereby providing minimum lower height of thecollapsed hoist so as to allow ready hoist access to the underbody of avehicle. The raising action of the hoist places the ram 13 underconstant load and in order to ensure the ram remains under constant andsmooth load during the whole of the raising action, the raising arms 9are provided with stops or collets 10 which prevent the raising arms formoving beyond their overcenter position, thereby ensuring that the hoistdoes not move beyond its maximum height and keeps the ram under constantload until the required height is achieved when the load can be relievedby activation of a locking mechanism as previously described.

Referring now to FIGS. 12 to 15, the retractable wheel means of thehoist are shown in some detail and can be seen to comprise a housing 8pivotally or swiverly connected to the lower chassis 2 around the wheelram body 37 so as to provide the wheel with the general rotational orswivel action to ensure complete horizontal mobility of the hoist. Thewheel means are retractable from a first raised position with the hoistlifted off the ground to a second lower position with the hoist lowereddown onto the ground by way of contact with the wheel housing 8. Thewheel 7 comprises twin wheel casters which are pivotally attached at 34to one end of an arm 32 which is in turn-pivotally connected at 35 atthe other end to an intermediate position on the housing 8. The arm canbe activated by way of a ram 38 which bears down upon an intermediateposition along the arm and causes the arm to move between a raisedposition and a lowered position so as to provide mobility for the hoistor provide the hoist with a firm seating on the ground or floor wherethe bottom of the wheel housing 8 sits firmly on the floor. The raisedand lowered positions can be seen in clear contrast by comparing FIGS.12, 14 and 13 and 15 as required.

Reverting back to FIG. 2, a plan view of the hoist sliding rubber blocks4 are positioned at each of the comers of the upper platform 1 and areslidable along channels 5 so as to accommodate any particular vehiclebeing mounted on the hoist. The particular details of the sliding rubberblocks are shown in FIGS. 6 to 8.

The invention provides for the first time a compact vehicle body hoistcapable of readily lifting a motor vehicle body to a height of about 1meter or to a height any where in between and allowing a vehicle soraised to be readily manipulated and moved around a floor area withoutfear of instability. In this manner the hoist can be used as a mechanismfor raising a vehicle body in its entirety above a workshop floor toallow ready access for work underneath or can also be used as amechanism for lifting a vehicle body in its entirely off the floor forthe purposes of shifting and general movement of that vehicle body abouta workshop in 360° direction within a very confined space. The raisingand lowering of the hoist is preferably activated by a hydraulic ramwhich can be powered by sources readily available to any workshop oralternatively can be electrically or otherwise activated with theprovision of batteries or mains power. Alternatively, the hoist could ofcourse be activated by manual jacking mechanism if necessary and in allrespects, the hoist provides a highly simplified compact rugged,reliable and substantially safe means of raising and manipulating wholevehicle bodies with a minimum of machinery. The hoist can be provided invarious sizes although a footprint of the hoist will generally occupybetween 20 and 60% of the footprint of a vehicles wheels so as toprovide adequate stability, Dependant on the size of the hoist andvehicle involved, the hoist can be positioned front to rear or side toside of a vehicle in order to accommodate particular movements,stability or offset allowances for a vehicles particular position. Thehoist is readily operatable by an unaided operator and provides for oneoperator, the means to safely manipulate a vehicle to virtually anyrequired position. The locking mechanism of the hoist allows a pluralityof hoist units to be used with only one hydraulic system which can bemoved from one hoist to the other once a hoist has been raised to itsdesired height and locked.

When not in use, the hoist forms a compact unit which can be readilystored on a wall or in another out of the way position in a workshop,thereby ensuring that minimum workshop space is taken up with additionalmachinery. The hoist is virtually maintenance free except for thenecessary and routine maintenance of the auxiliary hydraulics and pivotsand accordingly, a workshop can be provided with a plurality of hoistsof the above invention for a minimum of outlay whilst providing amaximum of use of a given workshops floor space and man power.

Accordingly, the invention provides for the first time a fully mobilehoist for raising, manipulating and handling motor vehicles. Rather thanhaving to rely on the prior art collection of available hoistingmechanisms which only facilitate the temporary movement or raisingelevation or manipulation of a vehicle, the current invention provides ameans of not only mobilising a damaged vehicle, but also enables a widerange of manipulation of such a vehicle to allow the vehicle to beraised to a variety of heights to facilitate work. It also provides aready mechanism for a motor vehicle to be raised and moved aroundreadily without any further aid about a workshop floor in a totally safemanner and in a way that once the correct position has been located, thevehicle and hoist can be lowered down onto the ground in a perfectlysafe fashion.

What is claimed is:
 1. A hoist for a vehicle comprising a chassis memberadapted for contact with a substrate upon which the hoist is located andbeing of a size sufficient to support the vehicle in a stable conditionon the substrate when the vehicle is in a raised position, said chassismember including a wheel assembly movable between a first configurationfor allowing the wheel assembly to be extended to enable movement of thehoist over the substrate and a second configuration for allowing thewheel assembly to be retracted so that the chassis member is in contactwith the substrate thereby preventing unwanted movement of the hoistwith respect to the substrate, and a platform member movable between afirst position for allowing the hoist to be placed under the vehicle andat least one of a plurality of second positions for supporting thevehicle in one or more raised positions above the substrate, saidplatform member capable of moving in substantially coplanarrelationships to the chassis member to raise or lower the vehicle,wherein, when the wheel assembly is in the first configuration and theplatform member is in one of the second positions supporting the vehiclein one of the raised positions, the hoist can be moved from one locationto another location over the substrate while maintaining the vehicle onthe platform member in a stable condition, and wherein when the wheelassembly is in the second configuration and the platform member is inone of the second positions supporting the vehicle in one of the raisedpositions, the hoist is prevented from unwanted movement over thesubstrate, thereby maintaining the vehicle immobile in the raisedposition, and further wherein the wheel assembly includes at least oneretractable wheel connected to the chassis member in such a manner as toallow movement of the hoist in all directions over the substrate, andthe hoist further comprising a locking means for maintaining theplatform member in at least one of the raised positions with respect tothe chassis member.
 2. A hoist according to claim 1 in which said atleast one wheel is connected to the chassis member in such a way as toallow said at least one wheel to swivel with respect to the chassismember in order to provide movement of the hoist in 360° over thesubstrate.
 3. A hoist according to claim 2 in which said at least onewheel includes a castor wheel system having a swivel housing connectedto the chassis member for allowing movement of the hoist in alldirections over the substrate.
 4. A hoist according to claim 1 in whichthe wheel assembly includes a plurality of retractable wheels in whichthe wheels are retracted when in the second configuration so that thechassis member rests on the substrate in use of the hoist to immobilizethe hoist against unwanted movement over the substrate.
 5. A hoistaccording to claim 4 in which the retractable wheels are extended whenin the first configuration thereby raising the hoist to be clear of thesubstrate to allow the wheels to contact the substrate in use of thehoist to allow 360° movement of the hoist over the substrate.
 6. A hoistaccording to claim 5 in which the retractable wheels are swivellyconnected to the chassis member to allow the hoist to be readily movedacross the substrate or to be supported on the substrate as required, bymoving the wheels between the two configurations, said retractablewheels including a wheel housing adapted for pivotal swivel fitting tosaid chassis member and an arm pivoted at one end to the housing andhaving the retractable wheels fitted to the other end wherein the armcan be moved between a raised position elevating said housing above saidsubstrate so as to extend the wheels for contact with the substrateallowing movement of the hoist and a retracted position in which thewheels are retracted so that the housing rests upon the substratethereby preventing movement of the hoist with respect to the substrate.7. A hoist according to claim 6 in which the retractable wheels aremoved between said raised and lowered positions by the action of a ram,said ram including a ram body and a piston wherein said wheel housingpivots about said ram body and said piston co-operates with said arm tomove the arm between said raised and retracted positions thereby movingthe wheels.
 8. A hoist according to claim 1 in which the substrate isthe floor of a workshop, garage, or factory.
 9. A hoist according toclaim 1 in which the size of the chassis member corresponds to thefootprint of the hoist and the footprint of the hoist is at least 20%,preferably from 20% to 60%, of the footprint of the vehicle to be raisedby the hoist.
 10. A hoist according to claim 1 in which the lockingmeans includes an elongate locking arm telescopically received through acollar arrangement in which one end of the locking arm is pivotallyconnected to one end of the chassis member and the collar is pivotallyconnected to one end of the platform member wherein the end of thechassis member to which the locking arm is connected is the opposite endto the end of the platform member to which the collar is connected suchthat telescopic movement of the arm through the collar moves theplatform member with respect to the chassis member.
 11. A hoistaccording to claim 10 in which the locking means is a pawl fitted tosaid collar and biased to intercept the travel path of the locking armso as to co-operate with one or a plurality of steps formed along thelength of the locking arm and to arrest the backward movement of thelocking arm through the collar.
 12. A hoist according to claim 11 inwhich the steps are indentations formed at spaced apart locations insaid locking arm for receiving said pawl to lock the position of theplatform member with respect to the chassis member.
 13. A hoistaccording to claim 12 in which the pawl co-operates with the locking armsteps by an overcentre movement such that once said pawl has engaged astep and arrested the backward movement of said locking arm, said pawlis released only after the locking arm has moved forward to allow saidpawl sufficient space to move overcentre and withdraw from the step. 14.A hoist according to claim 1, wherein: the chassis member furtherincludes a first framework arrangement defining the perimeter of thechassis member, the platform member includes a second frameworkarrangement defining the platform member, said platform member movablebetween said first position enabling the hoist to be placed under thevehicle in which the platform member is located in contact with thechassis member and at least one of the plurality of second positionssupporting the vehicle in one or more raised positions above thesubstrate in which the platform member is raised above the chassismember, and the hoist further includes: an extendable ram connectedbetween the chassis member and the platform member to move the platformmember relative to the chassis member, and a locking arrangementinterconnecting the platform member and the chassis member formaintaining the platform member in one of the second positionssupporting the vehicle in one of the raised positions.
 15. A hoistaccording to claim 14 further including: a plurality of arms to supportthe platform member in the plurality of second positions supporting thevehicle in one or more raised positions in accordance with movement ofthe platform member by the ram, wherein each arm includes: a firstportion connected to the platform member, and a second portion rotatablyconnected to the chassis member to enable rotation of that arm relativeto the chassis member, wherein the arms rotate to support the platformmember in the substantially coplanar relationships with the chassismember in accordance with platform member movement between the first andplurality of second positions.
 16. A hoist according to claim 15,wherein: the first framework arrangement of the chassis member includesa rectangular configuration with an open interior, wherein the secondportion of each arm is rotatably connected to the chassis member towarda respective first framework arrangement corner, and the secondframework arrangement of the platform member includes a rectangularconfiguration with an open interior, wherein the first portion of eacharm is connected to the platform member toward a respective secondframework arrangement corner.